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Transcript
2.2. Respiration summary 2.2.5 - H.L 2.2.10 Respiration At the end of ths section you should be able to …. 1. Define the term: aerobic respiration. 2. Explain the role of aerobic respiration 3. Express aerobic respiration by a balanced equation. 4. Know respiration is a 2 stage process 5. Know stage 1 does not require oxygen and releases a small amount of energy, occurs in cytosol 6. Know Stage 2 does require oxygen and releases a large amount of energy, occurs in mitochondrion 7. Define anaerobic respiration. Know it is a first stage process 8. State the products of anaerobic respiration 9. State the cellular location of the first & second stage. Contemporary issue 10. Explain the role of microorganisms in fermentation including bioprocessing with immobilised cells: procedure, advantages and use in bioreactors H.L.2.2.10 11. Know the first stage reaction: Glycolysis 12. Know the fermentation option: alcohol and carbon dioxide or lactic acid production 13. Know the second stage process: details of Krebs cycle and electron transport system Mandatory activity: Prepare & show the production of alcohol by yeast Key words Aerobic respiration, anaerobic respiration, cytosol, fermentation, bioreactor, sodium alginate, calcium chloride, glycolysis, iodoform, potassium iodide, sodium hypochlorite 1 2.2. Respiration summary Definition of aerobic respiration: Controlled release of energy from food using oxygen. Role of aerobic respiration: Provide energy for cellular activity e.g. protein synthesis, DNA replication, and cell division. Provides carbon dioxide for photosynthesis. Balanced equation: C6H12O6 + 6O2 = 6CO2 + 6H2O + energy. Stages of respiration Respiration is a two stage process: The first stage does not require oxygen and releases a small amount of energy; The second stage does require oxygen and releases a large amount of energy. Note: Further detail on stages 1 and 2 under higher level P 3 First stage process Anaerobic respiration may occur in the presence of oxygen but does not use oxygen. It is therefore a first-stage process. Anaerobic respiration is also known as Fermentation. The products of Fermentation (anaerobic respiration) are lactic acid or alcohol and carbon dioxide. Fermentation (Anaerobic respiration): Glucose alcohol + carbon dioxide. or Glucose Lactic acid. Second-stage process Aerobic respiration uses oxygen and is described as a second-stage process. C6H12O6 + 6O2 = 6CO2 + 6H2O + energy. Cellular location of the first and second stage process: The first stage process occurs in the cytosol (the cytoplasm minus the organelles). The second stage process occurs in the mitochondrion. 2 2.2. Respiration summary Contemporary issue: Role of micro-organisms in industrial fermentation Industrial fermentation: The use of micro-organisms to make a product e.g. alcohol or bread Also known as bioprocessing Carried out on a large scale in vessels called bioreactors. Can be carried out using immobilized enzymes (cells). Enzymes are attached to an inert material e.g. sodium alginate Procedure 1. 2. 3. 4. 5. Yeast is mixed with a sodium alginate . Drops of the mixture are added to a calcium chloride solution. Small beads with live, trapped yeast are formed. Nutrients can diffuse through the beads to the live yeast. The product will diffuse from the yeast . Advantages of Immobilised Enzymes Sodium alginate with entrapped enzyme Uses of immobilised enzymes (cells) To make alcohol To produce glucose To make lactose-free milk 3 1. Easy recovery of enzymes for reuse. 2. Easy recovery of products (no enzyme contamination). 3. Greater enzyme stability. 2.2. Respiration summary H. 2.2.10 Higher level STAGE 1: GLYCOLYSIS The first stage process is referred to as Glycolysis Converts a six-carbon carbohydrate (glucose) to pyruvate with the generation of a small amount of ATP. Under anaerobic conditions: the pyruvate molecule is converted or reduced to alcohol and carbon dioxide in most plant cells and yeast. or the pyruvate molecule is reduced to lactic acid in most animal cells and many bacteria STAGE 2: KREBS CYCLE/ELECTRON TRANSPORT SYSTEM In the second stage process under aerobic conditions, a series of reactions occurs: the pyruvate molecule enters the mitochondrion and is broken down to one molecule of carbon dioxide and a two-carbon acetyl group, acetyl Co-enzyme A. This Acetyl Co A enters a series called Krebs Cycle and leaves it later as CO2 and H2O. During this cycle an electron transport system operates to remove electrons from the substrate intermediates Electrons from the cycle are transferred through an electron transport chain (inner membrane of mitochondrion) Ultimately these are transferred to oxygen which combines with hydrogen to form water The energy released by these electrons through the chain is used in the production of ATP molecules (a large amount of energy is produced). Note: The electron transport system cannot work in the absence of oxygen. 4 2.2. Respiration summary i) PREPARE AND (ii) SHOW THE PRODUCTION OF ALCOHOL BY YEAST MATERIALS/EQUIPMENT Yeast Glucose Sodium hypochlorite solution Potassium iodide solution Fermentation locks DIAGRAM (i) To prepare alcohol using yeast PROCEDURE (i) To prepare alcohol using yeast 1. Add yeast and glucose to conical flask A. 2. Add glucose to flask B. This acts as a control . 3. Attach a fermentation lock to each flask. 4. Place both flasks in the incubator at 30 oC overnight. (ii) To show the presence of alcohol: Iodoform test for alcohol 1. Filter the contents of each flask into test tubes. 2. To each test tube, add potassium iodide solution and sodium hypochlorite solution. 3. Transfer to a water bath for 4-5 minutes. 4. Allow to cool. 5. Record and compare results. 6. Replicate the investigation. A Yeast and glucose Results Flask Yeast and glucose solution Control (no yeast) Original colour of filtrate Clear Final colour filtrate Clear Clear Yellow crystals 5 B Glucose (control)